Cantilevered rotor pump and methods for axial flow blood pumping

ABSTRACT

Blood pump devices having improved rotor design are provided herein. Such blood pump devices include rotors having cantilevered support through a sealed mechanical bearing disposed outside a blood flow path of the device so as to avoid thrombus formation caused by blood contact with the bearing. The bearing means can be rotatably coupled with a proximal portion of the rotor shaft extending outside the fluid path, while a stator drives rotation of the rotor shaft so that one or more rotor blades on a distal portion of the rotor force blood flow through the device. The bearing means may include one or more radial bearings on a proximal portion of the rotor shaft that are isolated from the blood flow path by one or more rotary seals.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/195,258, filed on Jul. 21, 2015, and entitled “CANTILEVERED ROTORPUMP AND METHODS FOR AXIAL FLOW BLOOD PUMPING,” the entirety of which ishereby incorporated herein by reference.

This application relates generally to U.S. application Ser. No.14/489,041 entitled “Pump and Method for Mixed Flow Blood Pumping” filedSep. 17, 2014; U.S. application Ser. No. 13/273,185 entitled “PumpingBlood” filed Oct. 13, 2011; each of which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND

This application relates generally to mechanical circulatory supportsystems, and more specifically relates to improved rotor designs inaxial flow blood pumps.

Ventricular assist devices, known as VADs, are implantable blood pumpsused for both short-term (i.e., days, months) and long-term applications(i.e., years or a lifetime) where a patient's heart is incapable ofproviding adequate circulation, commonly referred to as heart failure orcongestive heart failure. According to the American Heart Association,more than five million Americans are living with heart failure, withabout 670,000 new cases diagnosed every year. People with heart failureoften have shortness of breath and fatigue. Years of living with blockedarteries or high blood pressure can leave your heart too weak to pumpenough blood to your body. As symptoms worsen, advanced heart failuredevelops.

A patient suffering from heart failure, also called congestive heartfailure, may use a VAD while awaiting a heart transplant or as a longterm destination therapy. In another example, a patient may use a VADwhile recovering from heart surgery. Thus, a VAD can supplement a weakheart (i.e., partial support) or can effectively replace the naturalheart's function. VADs can be implanted in the patient's body andpowered by an electrical power source inside or outside the patient'sbody.

While blood pumps have been effective for many patients, becausepatients using such devices are living longer, further improvements thatprolong the effectiveness and lifetime of such blood pump devices aredesired. One challenge frequently encountered in axial blood pumps isthe development of thrombus in the bearing assemblies supporting therotor. Thus, there is a need for improved blood pump designs that avoidthrombus formation over the lifetime of the device.

BRIEF SUMMARY

An axial flow mechanical circulatory support system having an improvedrotor design with resistance to thrombus formation is provided herein.

In one aspect, blood pumps having improved rotor designs that aresupported by mechanical bearings that avoid contact with blood aredescribed herein. In some embodiments, such improved blood pumpsinclude: a pump housing defining a blood flow passage; a rotor includinga rotatable shaft and one or more rotor blades extending laterally fromthe rotatable shaft within the blood flow path to facilitate flow ofblood upon rotation of the rotor; and a rotation means adapted fordriving rotation of the rotatable shaft. Advantageously, the rotor canbe rotatably coupled to the housing through a sealed mechanical bearingthat remains outside the blood flow path such that blood contact withthe bearing is avoided, thereby avoiding formation of thrombus on thebearing assembly and avoiding the need for washing or flushing thebearing with blood fluid or saline fluid. Typically, the rotation meansincludes a stator motor and the rotatable shaft includes a number ofmagnetic elements driven by the stator. In some embodiments, the bearingassembly is rotatably coupled with the rotor shaft at or near theproximal end of the rotor shaft that extends outside of the blood flowpath while a distal portion of the rotor shaft remains within the bloodflow path and free from attachment to the pump housing such that themechanical bearing provides cantilevered support of the rotor duringoperation.

In one aspect, the bearing assembly is rotatably coupled with the rotorshaft along a proximal portion of the rotor shaft axially separated froma distal portion from which the one or more rotor blades extend. In someembodiments, the bearing assembly is axially separated from the one ormore rotor blades by a separation distance, such as between 0.1 and 10cm, or more preferably between 0.25 cm and 5 cm. In some embodiments,the rotor includes comprises a series of rotor blades that aredistributed circumferentially about the rotor. The rotor blades, rotorand/or the rotor shaft may be formed of different materials or the samematerials and may be assembled from separate parts or integrally formed.

In some embodiments, the rotor is disposed substantially or entirelywithin the pump housing during operation of the device. The rotor may beassembled by removal of a rear cover of the housing, the rear coverincluding a circular hole through which a proximal portion of the rotorshaft extends before attachment to the bearing assembly. In someembodiments, the mechanical bearing assembly resides within a cavity inthe rear cover isolated from the blood flow path within the housing. Oneor more rotary seals may be used to fluidly-seal the mechanical bearingfrom any contact with blood.

In one aspect, the rotor shaft is substantially rigid and extendsdirectly from the sealed bearing assembly to the rotor blades within theblood flow path defined by the pump housing. In some embodiments, therotor is sufficiently rigid so as to inhibit lateral deflection of adistal portion of the rotor on which the one or more blades aredisposed. The rotor can be selected of a material sufficiently rigidsuch that a maximum lateral deflection during operation of the bloodpump is less than 0.1″, less than 0.01″ or less than 0.001″. The rotorblades may also be substantially rigid, semi-rigid, flexible or acombination of rigid and flexible components. Typically, the rotorblades are rigid or semi-rigid and are disposed in a substantially fixedposition and/or orientation relative the rotor shaft.

In another aspect, the sealed mechanical bearing assembly includes oneor more radial bearings. The one or more radial bearings may be selectedto have an axial thickness or width that extends along a longitudinalaxis of the rotor. The radial bearing may be of a metallic (e.g.stainless steel) and/or a ceramic construction. The bearing assembly mayinclude a lubricant, such as an oil-based or silicone lubricant, tofacilitate movement of the radial bearings within the assembly. Thisaspect allows the bearing to withstand greater deflecting forces and/orto apply a greater reactive torque to the proximal portion of the rotorshaft so as to maintain a position and/or alignment of the rotor duringoperation. In some embodiments, the one or more radial bearings have atotal axial width between 0.01″ and 1″, or more preferably between0.050″ and 0.500″. The length of the rotor may be between 0.250″ to3.500″. In some embodiments, the pump housing is substantially rigid andthe rotor blades are disposed entirely within the blood flow pathdefined within the pump housing. In some embodiments, the rotor isdriven by a drive shaft. The mechanical bearing may be incorporated intoa rear cover that interfaces with the pump housing and may also be ofrigid construction. In some embodiments, the drive shaft issubstantially rigid and may be entirely internal to the blood pump, suchthat the shaft is driven without any need for motors or cables externalto the blood pump to drive the rotor. In some embodiments, the rotorextends directly from the mechanical bearing to the rotor blades withinthe blood pump.

While it is appreciated that rotors of various sizes may be used, thisdesign may utilize rotors of larger sizes, including rotors having anouter diameter in excess of 9 mm to facilitate higher blood flow rates.In some embodiments, the blood pump is adapted to pump blood at a flowrate of greater than 3.5 L/min at normal physiological pressure. In someembodiments, the blood pump is adapted to pump greater than 4 L/min, 5L/min, 6 L/min, 7 L/min, 8 L/min, 9 L/min or 10 L/min. In someembodiments, normal physiological pressure is 60 mm Hg, while in otherembodiments, normal physiological pressure is 30 mm Hg. In some aspects,normal physiological pressure can be 10 to 30 mm Hg for the rightventricle and 10 to 100 mm Hg or greater for the right ventricle.

In some embodiments, such devices are configured with rotors dimensionedto provide a suitable blood flow rate to provide ventricular assistwhile rotational speeds of the rotor are within a range of about 1,000to 10,000 rpm, such as within a range of about 1,000 to 5,000 rpm. Insome examples, suitable blood flow rates are any blood flow rate up to10 L/min, and are often within a range of blood flows such as between 1L/min to 12 L/min, between 3 L/min to 10 L/min, and 4 L/min to 6 L/min.Such rotors can be controlled so as to provide constant flow rates orvariable flow rates as needed. It is appreciated that such pump devicescan be controlled so as to provide lower blood flow rates as needed, forexample depending on the level of assist required by the blood flowpump.

In another aspect, the rotor is supported at a first end by a bearingassembly and includes one or more rotor blades at a second end oppositethe first end that is unsupported such that the rotor is cantilever. Insome embodiments, the first end is incorporated into an implanteddevice. In some embodiments, the rotor is supported only at the firstend of the rotor.

In another aspect, such devices include one or more rotary sealsdisposed along the rotor shaft between the bearing assembly and the oneor more rotor blades so as to fluidly seal the bearing assembly from anyblood flowing through the blood flow path. In some embodiments, a bloodpump includes a housing with an inner wall defining an inlet, an outletdownstream from the inlet, and a blood flow path between the inlet andthe outlet. A rotor extending between a proximal and distal end, whichextends distally into the blood flow path and includes magnetic materialto facilitate being rotationally driven by a stator. A motor statorpositioned about the blood flow path defined at least in part by thepump housing between the inlet and the outlet of the pump. The motorstator, during operation, is configured to generate a magnetic field forrotating the rotor to force blood along the blood flow path by rotationof one or more rotor blades along a distal portion of the rotor. Amechanical bearing assembly is disposed outside the blood flow path androtatably couples a proximal portion of the rotor with the pump housing.

Methods of pumping blood in accordance with aspects of the invention arealso provided. In some embodiments, such methods include operating ablood pump so as to transport blood along a blood flow path through ablood flow pump. Operating the blood pump may include rotating a rotorby use of a stator extending about the blood flow path so that movementof one or more rotor blades on a distal portion of the rotor forcesblood along the blood flow path; and maintaining a position and/oralignment of the rotor during rotation by rotatably securing the rotorwith a mechanical bearing disposed outside the blood flow path therebyinhibiting thrombus formation in the bearing. Some methods can furtherinclude sealing the mechanical bearing from the blood flow path with aradial seal extending about the rotor between the mechanical bearing anda distal portion of the rotor having the one or more rotor blades incontact with blood along the blood flow path. In some embodiments,alignment of the rotor within the blood flow path is maintained byresisting lateral applied forces from blood flow by applying acountering torque through the one or more radial bearings. Typically,the radial bearing is disposed at or near one end of the rotor such thatthe countering torque is cantilevered through the rotor.

In another aspect, the invention provides an implantable pump having acantilevered rotor and a sealed bearing assembly. Such pumps can includea pump housing defining a flow passage therethrough and a cantileveredrotor having a rotatable shaft and extending at least partly within theflow passage to facilitate fluid flow through the passage upon rotationof the rotatable shaft. The rotor can include one or more rotor blades,fins, depression, or various other features as needed to facilitatefluid flow upon rotation of the shaft. The sealed bearing assemblysupportingly couples the rotatable shaft within the pump and is sealedfrom contact with fluid flowing through the flow passage duringoperation of the pump. In some embodiments, the bearing assembly isdisposed at or near one end of the rotor such that the rotatable shaftis cantilevered. The bearing assembly can be disposed outside the flowpath defined by the pump housing. The bearing assembly typicallyincludes lubricant sealed within. Since the bearing assembly is sealedfrom its environment, the bearing assembly can include one or morebearing components and/or lubricants that are non-biocompatible. Thebearing assembly can also include sealed within one or moreoff-the-shelf shelf bearing components that are standard fornon-implantable applications or various types of pumps. The mechanicalbearing assembly can also be sealed without any fluid channel forflushing the bearing assembly.

In yet another aspect, such pumps can include a cantilevered rotor thatextends along a first axis and a fluid flow path defined to direct fluidalong the first axis and divert fluid flow along one or more other axes,such as a second axis that is transverse to the first axis. In someembodiments, the first and second axes are substantially perpendicular.Such pumps can be configured as a blood pump, the mechanical bearingassembly being sealed from blood flowing through the flow passage so asto inhibit thrombus formation by avoiding contact between the bearingassembly and any blood flowing through the flow passage. In suchembodiments, the pump can be configured such that a flow inlet of thepump directs fluid from a ventricle of the heart along the first axis,during rotation of the cantilevered rotor, while the flow path divertsblood flow along a second axis that is transverse to the first axis to aflow outlet for delivery to the aorta.

The terms “invention,” “the invention,” “this invention” and “thepresent invention” used in this patent are intended to refer broadly toall of the subject matter of this patent and the patent claims below.Statements containing these terms should be understood not to limit thesubject matter described herein or to limit the meaning or scope of thepatent claims below. Embodiments of the invention covered by this patentare defined by the claims below, not this summary. This summary is ahigh-level overview of various aspects of the invention and introducessome of the concepts that are further described in the DetailedDescription section below. This summary is not intended to identify keyor essential features of the claimed subject matter, nor is it intendedto be used in isolation to determine the scope of the claimed subjectmatter. The subject matter should be understood by reference toappropriate portions of the entire specification of this patent, any orall drawings and each claim. The invention will be better understoodupon reading the following description and examining the figures whichaccompany it.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, aspects, and embodiments of the invention will bedescribed by way of example only and with reference to the drawings. Inthe drawings, like reference numbers are used to identify like orfunctionally similar elements. Elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.

FIG. 1 is an illustration of a mechanical circulatory support systemimplanted in a patient's body in accordance with embodiments of theinvention.

FIG. 2 shows a conventional axial blood flow pump device.

FIG. 3 shows an axial flow blood pump device with an improved rotordesign in accordance with some embodiments.

FIG. 4 shows another axial flow blood pump device with an improved rotordesign in accordance with some embodiments.

FIG. 5 shows another axial flow blood pump device with an improved rotordesign in accordance with some embodiments.

FIGS. 6-7 shows methods of pumping blood with a blood pump in accordancewith some embodiments.

DETAILED DESCRIPTION

FIG. 1 is an illustration of a mechanical circulatory support system 10implanted in a patient's body 12. The mechanical circulatory supportsystem 10 comprises an implantable blood pump 14, outflow cannula 18,system controller 20, and power sources 22. The implantable blood pump14 may comprise a VAD that is attached to an apex of the left ventricle,as illustrated, or the right ventricle, or both ventricles of the heart24. The VAD is typically an axial flow pump as described in furtherdetail herein that is capable of pumping the entire output delivered tothe left ventricle from the pulmonary circulation (i.e., up to 10 litersper minute). Related blood pumps applicable to the present invention aredescribed in greater detail below and in U.S. Pat. Nos. 5,695,471,6,071,093, 6,116,862, 6,186,665, 6,234,772, 6,264,635, 6,688,861,7,699,586, 7,976,271, 7,997,854, 8,007,254, 8,152,493, 8,652,024, and8,668,473 and U.S. Patent Publication Nos. 2007/0078293, 2008/0021394,2009/0203957, 2012/0046514, 2012/0095281, 2013/0096364, 2013/0170970,2013/0121821, and 2013/0225909, all of which are incorporated herein byreference for all purposes in their entirety. The blood pump 14 may beattached to the heart 24 via a ventricular cuff which is sewn to theheart 24 and coupled to the blood pump 14. The other end of the bloodpump 14 connects to the ascending aorta via the outflow cannula 18 sothat the VAD effectively diverts blood from the weakened ventricle andpropels blood to the aorta for circulation to the rest of the patient'svascular system.

FIG. 1 illustrates the mechanical circulatory support system 10 duringbattery 22 powered operation. A driveline 26 which exits through an exitsite 28 in the patient's abdomen, connects the implanted blood pump 14to the system controller 20, which monitors system 10 operation. Relatedcontroller systems applicable to the present invention are described ingreater detail below and in U.S. Pat. Nos. 5,888,242, 6,991,595,8,323,174, 8,449,444, 8,506,471, 8,597,350, and 8,657,733 and U.S.Patent Publication Nos. 2005/0071001 and 2013/0314047, all of which areincorporated herein by reference for all purposes in their entirety. Thesystem may be powered by either one, two, or more batteries 22. It willbe appreciated that although the system controller 20 and power source22 are illustrated outside/external to the patient body, the driveline26, system controller 20 and/or power source 22 may be partially orfully implantable within the patient, as separate components orintegrated with the blood pump 14. Examples of such modifications arefurther described in U.S. Pat. No. 8,562,508 and U.S. Patent PublicationNo. 2013/0127253, each of which is incorporated herein by reference inits entirety for all purposes.

In some conventional blood pumps, the rotor is suspended by bearingassemblies near opposite ends of the rotor with the rotor bladesbetween. The bearings are disposed within the blood flow path andlubricated, in part, by blood flowing across the bearings. Such bearingsare known as blood-washed bearings.

An example of such bearings can be understood by referring to FIG. 2,which shows a conventional axial flow blood pump 100′. The pump includesa housing 110′ that defines a blood flow path 112′. Blood enters thehousing 110′ through an inlet 101′, passes through a central tubularregion 102′ of the housing 110′, and exits through an outlet 103′. Thehousing 110′ contains a motor stator 128′, which drives rotation of arotor 120′ located in the blood flow path 112′. As the rotor 120′rotates, blades 122′ on the rotor 120′ impart energy to the blood flow,resulting in pressure and blood flow at the outlet 103′. The rotor 120′is suspended in the housing 110′ by fore and aft mechanical,blood-immersed bearings 124′, 126′ that limit axial translation of therotor 120′. The bearings 124, 126 also limit the rotor from shifting offits axis of rotation and resist various destabilizing forces that occurduring operation.

Studies have revealed that blood-washed bearings tend to developthrombus over-time at the point of contact between the bearing ball andthe cup in which the ball resides. Development of thrombus in thebearings can significantly degrade performance of the pump over time. Intwelve chronic in-vivo animal studies, upon completion of the studies,the pumps were explanted and disassembled, after which it was observedthat, in 50% of the pumps, either one or both bearings had some level ofthrombosis evident.

To address these issues, recent developments include replacing bloodwashed mechanical bearings in rotary blood pumps that are used tosuspend rotors with actively/passively magnetically suspended rotors.This allows for the removal of mechanical bearings in pumps, however,the magnetic levitation of the rotor creates hydrodynamic bearingsbetween the pump housing and rotor. In addition, adding magnetics toVAD's significantly increases the complexity of the design and itsoperation since the magnets must generally maintain a radial positionwithin the blood flow path as well as a longitudinal position. Due inpart to these complexities, current versions of hydrodynamic bearingsused in VAD's still frequently develop thrombus issues.

In one aspect, the invention addresses these challenges associated withconventional designs by reconfiguring the blood pump to includemechanical bearings that are excluded from the blood flow path. In someembodiments, the mechanical bearing is excluded from the blood flow pathby use of a cantilevered rotor design in which the rotor is supported atone end by a mechanical bearing assembly that remains sealed outside ofthe blood flow path. In one aspect, the mechanical bearing assembly issealed such that there is no need for washing the bearing with bloodflow or flushing the assembly with saline. The mechanical bearingassembly can include one or more radial bearings at or near one end ofthe rotor, thereby providing cantilevered support during rotation of therotor. In some aspects, the radial bearing can be of a metallic (e.g.stainless steel) or non-metallic (e.g. ceramic, polymer) construction.In one aspect, the design allows for the rotor to operate with a singlefluid flow path for blood flow through the blood pump, without the needfor additional fluid flow paths for saline flushing or waste return. Inaddition, by reconfiguring the design of the axial flow pump, theblood-washed mechanical ball and cup bearing design used in conventionalaxial pump designs can be eliminated. As a byproduct, the inlet stator,front bearing set, and rear bearing set can be removed from the design.

FIG. 3 illustrates an exploded view of an embodiment of an axial bloodflow pump design with an improved cantilevered rotor design. Theimproved axial flow blood pump 100 includes a housing 110 that defines ablood flow path 112 that enters the housing 110 through an inlet 101,passes through a central tubular region of the housing and exits throughan outlet 103. Housing 110 may be non-magnetic and may be made of abiocompatible material such as titanium or a suitable ceramic materialwhich is non-thrombogenic, rigid, and exhibits minimum eddy currentlosses. Housing 110 contains a rotating means, such as a motor stator,adapted to drive rotation of rotor 120. Rotor 120 includes one or morerotor blades 122, typically a group of helical blades, on a distalportion that extends into the blood flow path 112. As rotor 120 rotates,rotor blades 122 impart energy to the blood flow, resulting in pressureand blood flow at the outlet 103. Rotor 120 is suspended in the housing110 by a mechanical bearing assembly 130 disposed on a proximal portionof rotor 120 that extends through a hole in the rear cover 11 outsidethe blood flow path.

In some embodiments, rotor 120 is redesigned such that a circular rotorshaft 121 that extends proximally from the rear of the rotor and outsidethe blood flow path. Such a configuration allows for use of atraditional mechanical bearing (not blood or saline washed). Mechanicalbearing 130 can be assembled within the rear cover 111 of the pumphousing 110 such that any contact with the blood flow stream is avoided.In this embodiment, the shaft of rotor 120 slides through back cover 111and can be press fit into the bearing assembly. At the shaft to pluginterface, a mechanical rotary seal can be used to further ensure bloodcontact is avoided. A design of this nature reduces the static todynamic interfaces from two to one. Furthermore, unlike blood washedbearings, this design does not rely on blood as a lubricant. Rotary sealkeeps the blood from being used as a lubricant, which allows blood to beeliminated as a lubricant within rotary type blood pump devices. Since asealed mechanical bearing assembly is used, this allows for a bearingdesign that utilizes various other types of lubricant (e.g. oil-based,silicone) and could use and/or adapt common bearings and lubricants fromthe mechanical arts as would be understood by one of skill from thedescription herein. Such mechanical bearings may provide improvedperformance and durability and increased life-times as compared tosaline purged or blood washed designs.

Since mechanical bearing 130 couples the rotor at only one end, itprovides cantilevered support and withstands lateral deflection of therotor by applying a torque through the proximal portion. In someembodiments, the mechanical bearing may be selected to have an axialthickness extending along an axis of the rotor shaft between 0.050″ to0.500″ to allow the bearing to withstand greater deflecting forces andapply greater reactive torques. In some embodiments, the device mayinclude a mechanical bearing 130 consisting of multiple stacked radialbearing, such as two stacked radial bearings, as shown in FIG. 4.

In another aspect, rotor 120 includes a fluid-tight seal 140 disposedbetween a proximal portion of the rotor coupled with mechanical bearingassembly 130 and a distal portion from which the rotor blades extendwithin the blood flow path. In some embodiments, such as that shown inFIG. 3, the rotary seal 140 comprises two interfacing components, firstcomponent 140 a that is secured to the rotor shaft and revolves with theshaft and second component 140 b that remains secured with rear cover111. Typically, first component 140 a is a flat component that engagesagainst second component 140 b, another component, so as to provide afluid-tight seal and inhibit blood flow into the bearing assembly. Oneor both of the first and second components 140 a, 140 b can be formed ofa hard and/or rigid material so as to withstand the variable forces thatmay occur during operation and maintain a fluid-tight seal over thelifetime of the device. Also, one or both of the seals may be attachedand/or interface with a compliant member in order to provide sealpreload and allow the seals to track on one another.

FIG. 4 shows another exemplary pump 200 having a cantilevered rotor 120in which the supporting mechanical bearing 130 is disposed outside theblood flow path. In this embodiment, mechanical bearing assembly 130includes two radial bearings stacked on the proximal portion of therotor 120. Rotor 120 includes permanent drive magnets 150 to facilitatebeing rotationally driven by a motor stator 151 having electricallyconductive coils. The coils are placed within an enclosure whichsurrounds the blood flow path and the rotor 120 disposed within pumphousing 110. The motor stator 151 serves to rotate rotor 120 by theconventional application of electric power to the coils to drive thepermanent drive magnets 150 incorporated into rotor 120. ElastomericO-rings 153 keep the magnets from rotating in the rotor. Such magnetsare selected for magnetic properties, length, and cross-sectional areain order to provide good electromagnetic coupling with the magneticforces created by the motor stator 151. In some embodiments, the motoris a three phase, brushless DC motor. In other embodiments, the motorcan be a toroidal, three phase or wye connected design. The stator mayhave a back iron design which is consistent with a typical radial fluxgap motor. If desired, motor stator 151 can be incorporated within aseparate, hermetically sealed enclosure that slides over pump housinginto position. In some embodiments, the body of rotor 120 includes amagnetically hard ferromagnetic material, i.e., a material which forms astrong permanent magnet and which is resistant to demagnetization. Thematerial of rotor body 120 is typically selected to be biocompatible andsubstantially non-thrombogenic. Rotor 120 can be formed as a unitarycomponent or can be formed of separate components joined together. Insome embodiments, the rotor body is formed as a unitary mass of asuitable material, such as an alloy of platinum, titanium, and cobalt.In other embodiments, the rotor body may be formed from a magnetic metalsuch as an iron-nickel alloy with an exterior coating of anothermaterial to increase the body's biocompatibility. Further detailsregarding suitable rotor designs are described in U.S. Pat. No.5,588,812; Ser. No. 62/084,946; 2016/0144089; 2014/0324165; and U.S.Pat. No. 9,265,870; each of which is incorporated herein by reference inits entirely for all purposes.

FIG. 5 shows another exemplary axial pump device 300 having acantilevered rotor 120 supported by a mechanical bearing 130. Thisembodiment includes a radial seal 140 that comprises a curvedelastomeric seal that spans the interface between the rotor shaft 121and the hole in the rear cover 111 through which the proximal portion ofthe rotor 120 extends. This configuration utilizes a flexibleelastomeric seal to direct the flow of blood away from the interface andmaintain a fluid-tight seal so as to isolate the mechanical bearing fromany contact with blood, thereby avoiding formation of thrombus. In oneaspect, since embodiments of the invention provide conditions thatreduce blood coagulation and thrombus formation, a lower amount ofanticoagulant may be used, which may result in fewer patient adverseside effects.

FIG. 6-7 show flowcharts of exemplary methods of pumping blood with ablood pump in accordance with embodiments of the invention. FIG. 6depicts a method of pumping blood that includes: operating a blood pumpso as to transport blood along a blood flow path defined by a housing ofthe blood flow pump. Operation of the pump is performed by rotating arotor of the pump by use of a stator extending about the blood flow pathso that movement of one or more rotor blades on a distal portion of therotor forces blood along the blood flow path. The method furtherincludes: maintaining a position and/or alignment of the rotor duringrotation by rotatably securing the rotor with a sealed mechanicalbearing disposed outside the blood flow path thereby inhibiting thrombusformation in the sealed mechanical bearing.

FIG. 7 depicts a method of pumping blood with a blood pump thatincludes: operating a blood pump so as to transport blood along a bloodflow path through a pump housing of the blood flow pump. Operation ofthe pump can be performed by rotating a rotor of the pump so thatmovement of one or more rotor blades within the blood flow path forcesblood along the blood flow path. The method further includes: isolatingblood moving along the blood flow path from a sealed bearing assemblysupporting the rotor at or near one end of the rotor, thereby avoidingblood contact and formation of thrombus within the bearing assembly.Isolating blood flow from the mechanical bearing assembly can beperformed by use of a radial seal or various other sealing means aswould be known to one of skill in the art.

While the above embodiments depict axial flow pump device, it isappreciated that the cantilever rotor design may be utilized in variousother rotary type blood pumps in accordance with the aspects describedherein. In addition, the radial seals may be applied to various otherembodiments to isolate various other bearing assembly designs from theblood flow path as desired. It is further appreciated that there are anynumber of mechanical bearing options that can be integrated within thedesigns described herein. For example, some embodiments may utilizeintegral duplex bearings and preloaded bearings that have increasedprecision. There are also many different types of bearing lubricationoptions available as well as rotary shaft seals that may be incorporatedinto various embodiments.

In alternative embodiments, aspects of the invention described above maybe used in centrifugal pumps. In centrifugal pumps, the rotors areshaped to accelerate the blood circumferentially and thereby cause bloodto move toward the outer rim of the pump, whereas in the axial flowpumps, the rotors are more or less cylindrical with blades that arehelical, causing the blood to be accelerated in the direction of therotor's axis.

In the foregoing specification, the invention is described withreference to specific embodiments thereof, but those skilled in the artwill recognize that the invention is not limited thereto. Variousfeatures and aspects of the above-described invention can be usedindividually or jointly. It is appreciated that any of the aspects orfeatures of the embodiments described herein could be modified, combinedor incorporated into any of the embodiments described herein, as well asin various other types and configurations of pumps. Further, theinvention can be utilized in any number of environments and applicationsbeyond those described herein without departing from the broader spiritand scope of the specification. The specification and drawings are,accordingly, to be regarded as illustrative rather than restrictive. Itwill be recognized that the terms “comprising,” “including,” and“having,” as used herein, are specifically intended to be read asopen-ended terms of art.

What is claimed is:
 1. An implantable blood pump comprising: a pumphousing defining a blood flow passage therethrough; a rotor including arotatable shaft and one or more rotor blades extending laterally fromthe rotatable shaft, wherein the rotor extends at least partly withinthe passage such that the one or more rotor blades are disposed withinthe blood flow path to facilitate blood flow through the passage uponrotation of the rotatable shaft, wherein the rotatable shaft isrotatably coupled within the pump housing through a sealed mechanicalbearing assembly disposed outside the blood flow passage so as toinhibit thrombus formation by avoiding contact between the bearingassembly and any blood flowing through the blood flow passage duringoperation of the blood pump; and a rotation means adapted for drivingrotation of the rotatable shaft.
 2. The blood pump of claim 1, whereinthe rotation means comprises a stator motor and the rotatable shaftincludes a number of magnetic elements.
 3. The blood pump of claim 1,wherein the rotor shaft extends between proximal and distal ends, thebearing assembly being rotatably coupled with the rotor shaft at or nearthe proximal end of the rotor shaft while a distal portion of the rotorshaft is disposed within the blood flow path.
 4. The blood pump of claim1, wherein the pump housing is substantially rigid.
 5. The blood pump ofclaim 1, wherein the bearing assembly is axially separated from the oneor more rotor blades by a separation distance between 0.25 cm and 5 cm.6. The blood pump of claim 4, wherein the rotor is rotatably coupledwith the pump housing through the proximal portion of the rotor shaftwhile the distal portion is free from attachment to the pump housing. 7.The blood pump of claim 1, wherein the bearing assembly is disposedoutside the blood flow path and sealed such that any bearing of thebearing assembly is free from contact with blood flowing through theblood flow path or any other fluid.
 8. The blood pump of claim 1,wherein the one or more blades comprises a series of blades.
 9. Theblood pump of claim 8, wherein series of blades are distributedcircumferentially about the rotor.
 10. The blood pump of claim 1,wherein the one or more blades and the rotor are formed of differentmaterials.
 11. The blood pump of claim 1, wherein the one or more bladesand the rotor are integrally formed.
 12. The blood pump of claim 1,wherein the rotor is disposed entirely within the pump housing duringoperation.
 13. The blood pump of claim 1, wherein the rotor shaft issubstantially rigid so as to inhibit lateral deflection of a distalportion of the rotor on which the one or more blades are disposed. 14.The blood pump of claim 13, wherein the rotor is sufficiently rigid suchthat a maximum lateral deflection during operation of the blood pump isless than 0.001″.
 15. The blood pump of claim 13, wherein the rotorblades are substantially rigid
 16. The blood pump of claim 15, whereinthe rotor blades have a substantially fixed position and orientationrelative the rotor shaft.
 17. The blood pump of claim 13, wherein therotor blades are flexible.
 18. The blood pump of claim 1, wherein thebearing assembly includes one or more radial bearings disposed on therotor shaft.
 19. The blood pump of claim 1, wherein the radial bearinghas an axial width between 0.050″ and 0.500″.
 20. The blood pump ofclaim 19, wherein a length of the rotor is between 0.250″ and 3.500″.21. The blood pump of claim 1, further comprising: a rotary sealrotatably disposed along the rotor shaft between the bearing assemblyand the one or more rotor blades so as to seal the bearing assembly fromany blood flowing through the blood flow path.
 22. The blood pump ofclaim 1, wherein the bearing assembly is disposed within a rear cover ofthe pump housing.
 23. The blood pump of claim 1, wherein the bearingassembly comprises radial bearings with a lubricant.
 24. The blood pumpof claim 23, wherein the radial bearings comprise are formed ofstainless steel or ceramic.
 25. The blood pump of claim 23, wherein thelubricant is an oil-based or silicone lubricant.
 26. The blood pump ofclaim 23, wherein the bearing assembly is sealed without any fluidchannel for flushing the bearing assembly.
 27. The blood pump of claim1, further comprising: a drive shaft driving rotation of the rotor,wherein the drive shaft is substantially rigid.
 28. The blood pump ofclaim 1, wherein the pump is an axial flow pump.
 29. A blood pumpcomprising: a housing with an inner wall defining an inlet, an outletdownstream from the inlet, and a blood flow path between the inlet andthe outlet; a rotor extending between proximal and distal ends, therotor including a magnetic material therein and extending distally intothe blood flow path; a motor stator positioned about the blood flow pathbetween the inlet and the outlet, the motor stator, during operation,configured to generate a magnetic field for rotating the rotor so as toforce blood along the blood flow path by rotation of one or more rotorblades along a distal portion of the rotor; and a sealed mechanicalbearing rotatably coupling a proximal portion of the rotor with the pumphousing, the sealed mechanical bearing being disposed outside of theblood flow path.
 30. A method of pumping blood with a blood pump, themethod comprising: operating a blood pump so as to transport blood alonga blood flow path through a pump housing of the blood flow pump, whereinoperating the blood pump comprises rotating a rotor by use of a statorextending about the blood flow path so that movement of one or morerotor blades on a distal portion of the rotor forces blood along theblood flow path; and maintaining a position and/or alignment of therotor during rotation by rotatably securing the rotor with a sealedmechanical bearing disposed outside the blood flow path therebyinhibiting thrombus formation in the sealed mechanical bearing.
 31. Themethod of claim 30 further comprising: sealing the mechanical bearingfrom the blood flow path with a radial seal extending about the rotorbetween the mechanical bearing and a distal portion of the rotor havingthe one or more rotor blades in contact with blood along the blood flowpath.
 32. The method of claim 30, wherein the mechanical bearingcomprises one or more radial bearings, the method further comprising:maintaining an alignment of the rotor within the blood flow path definedwithin the pump housing by resisting lateral applied forces from bloodflow by applying a countering torque through the one or more radialbearings.
 33. The method of claim 32, wherein the radial bearing isdisposed at or near one end of the rotor such that the countering torqueis cantilevered through the rotor.
 34. The method of claim 30, whereinrotating the rotor comprises lubricating the mechanical bearing assemblywith an oil-based or silicone lubricant without any lubrication providedby blood flowing through the pump.
 35. The method of claim 34, whereinthe mechanical bearing assembly is sealed without any fluid channel forflushing the bearing assembly.
 36. An implantable pump comprising: apump housing defining a flow passage therethrough; a cantilevered rotorhaving a rotatable shaft and extending at least partly within the flowpassage, the rotor being configured to facilitate fluid flow through thepassage upon rotation of the rotatable shaft; and a sealed bearingassembly supportingly coupling the rotatable shaft within the pump, themechanical bearing assembly being sealed from contact with fluid flowingthrough the flow passage during operation of the pump.
 37. Theimplantable pump of claim 36, wherein the bearing assembly is disposedat or near one end of the rotor such that the rotatable shaft iscantilevered.
 38. The implantable pump of claim 37, wherein the bearingassembly is disposed outside the flow path defined by the pump housing.39. The implantable pump of claim 36, wherein the cantilevered rotorextends along a first axis and the fluid flow path directs fluid alongthe first axis and diverts fluid flow along a second axis transverse tothe first axis.
 40. The implantable pump of claim 38, wherein the firstand second axis are substantially perpendicular.
 41. The implantablepump of claim 36, wherein the bearing assembly includes a lubricantsealed within.
 42. The implantable pump of claim 36, wherein the bearingassembly includes sealed within one or more bearing components and/orlubricants that are non-biocompatible.
 43. The implantable pump of claim36, wherein the bearing assembly includes sealed within one or moreoff-the-shelf shelf bearing components that are standard fornon-implantable applications.
 44. The implantable pump of claim 36,wherein the mechanical bearing assembly is sealed without any fluidchannel for flushing the bearing assembly.
 45. The implantable pump ofclaim 36, wherein the implantable pump is a blood pump and themechanical bearing assembly is sealed from blood flowing through theflow passage so as to inhibit thrombus formation by avoiding contactbetween the bearing assembly and any blood flowing through the flowpassage.